Make sure to initialize all fields in the special maps...

src/heap.cc

Index: src/heap.cc
===================================================================
--- src/heap.cc	(revision 3724)
+++ src/heap.cc	(working copy)
@@ -1185,7 +1185,10 @@
   reinterpret_cast<Map*>(result)->set_instance_type(instance_type);
   reinterpret_cast<Map*>(result)->set_instance_size(instance_size);
   reinterpret_cast<Map*>(result)->set_inobject_properties(0);
+  reinterpret_cast<Map*>(result)->set_pre_allocated_property_fields(0);
   reinterpret_cast<Map*>(result)->set_unused_property_fields(0);
+  reinterpret_cast<Map*>(result)->set_bit_field(0);
+  reinterpret_cast<Map*>(result)->set_bit_field2(0);

[Rico, 2010/01/28 08:14:48]

After adding the extensible property to bit_field2 maybe this needs to be (same
as in AllocateMap):
map->set_bit_field2(1 << Map::kIsExtensible);
(default value for extensible is true)

   return result;
 }